DMP

Distributed Music Player

The network protocol

Each message passed over the TCP control connection has the following format

A network packet
1 byte	4 bytes	1 byte	4 bytes	size bytes
encryption sentinel	possibly encrypted message::Type	encryption sentinel	size of message uint32_t	possibly encrypted message

• The encryption sentinels are either 0 or 1, for unencrypted and encrypted respectively.
• The Type is a uint32_t which can be casted to a message::Type
• The size of the message is a uint32_t and is the size of the message in bytes.
• The message is a custom Archive format, which serializes structs with boost::fusion.

For the time being all these components are sent separately resulting in 5 network packets. This is somewhat inefficient, it could be reduced quite easily to 1 packet when sending unencrypted and 2 packets when sending encrypted, due to way messages are currently handled. But it's not a priority until this becomes a performance bottle neck.

The serialization protocol

The Serialization archive format is straight forward. For each member of a struct serialize it members from top to bottom.

If the variable is

• a char, uint8_t int8_t cast it to a wider type and write it to avoid non printable characters.
• any other primitive, write the primitive.
• a string, write the length of the string followed by a space and the string itself.
• a container, write the size_t number of elements in the container followed by a space and serialize the elements.
• a pair or tuple, serialize all elements in order, space separated.

separate each type you have serialized with a space.

The encryption

DMP uses libsodium for encryption and password hashing for more information regarding the encryption used in the protocol specified above, please refer to libsodium

Building on Mac OSX

First we install the dependencies (for the client)

brew install icu4c taglib boost qt5 gstreamer libsodium gst-plugins-good
brew install gst-plugins-ugly --build-from-source

Then we can run cmake as usual. BUT: linking qt5 does not work out of the box (there is no macosx-clang binary in /usr/local/?). But one can set the following cmake options:

Qt5Core_DIR      /usr/local/Cellar/qt5/5.4.1/lib/cmake/Qt5Core
Qt5Gui_DIR       /usr/local/Cellar/qt5/5.4.1/lib/cmake/Qt5Gui
Qt5Widgets_DIR   /usr/local/Cellar/qt5/5.4.1/lib/cmake/Qt5Widgets